Just a comment, if I may. There are two ways (non-exhaustive list) to get good at math. One is to work in a high-energy physics lab. With 10,000 volt wires running around, if you make a mistake, you're dead. There are no small errors!
Similarly, another way to get good at math is to pretend someone's holding a gun to your head. If you make a mistake he's going to pull the trigger.
Seriously, though, mistakes are the gems of learning. Once you figure out why you made a mistake, and you invent a way to remember how not to make that mistake again, you've learned something truly valuable.